• Korean Journal of Fisheries and Aquatic Sciences
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• v.13 no.4
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• pp.195-206
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• 1980

Fish were grown in a water recycling rearing system consisting of a filter system, of which the area is about $30\;m^2$ and the volume of filter gravels is about $15\;m^3$, 6 rearing and 2 supplementary tans about $7\;m^2$ of surface area each. The results for 180 days from April 18 to October 14,1980 are summarized as following: One rearing tank was used for main experiment stocked with an equal number, and weight of each Israeli strain and $F_1$, hybrid between this strain and Korean local strain of common carp. Gross total production was 461 kg with a net production of 395 kg, and the Israeli strain grew to about 8 times initial weight and the hybrid about 6 times. Based on an analysis of results of the above mentioned main experiment and the other miscellaneous fish grown in the remaining tanks, it was considered to be feasible to implement a commercial production in this system by improving parts of the system and adding a number of the units. A special problem seems to be an adoption of more effective aeration device when fish loading increases. A solid waste removal system was deviced by use of by-pass flow ana this system worked very efficiently in view of supply water economy. A serious problem encountered in this experiment was heavy outbreaks of the gill-fluke, Dactylogyrus sp. which was relatively easily eradicated with Dipterex or DDVP treatment in the first trials, but later on strains which were resistant to any of these chemicals appeared.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.441-451
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• 2000

Sludge produced from water treatment plants contains plenty of aluminum due to addition of coagulants, polyaluminum chloride(PACI) which has been widely used in most of water treatment plants. however. the whole of PACI is imported from other countries. In this research. the effective methods for recycling PACI from sludge of water treatment plants were developed and evaluated. Aluminum chloride hexahydrate($AlCl_3{\cdot}6H_2O$) was obtained by sparging HCl gas aluminum extracted from sludge using hydrochloric acid (HCI). This aluminum chloride hexahydrate was solidified by decomposition at $180^{\circ}C$. and dissolved in water to produce PACI. The optimum extraction rate was obtained at the condition of 10 minutes of reaction time. $105^{\circ}C$ of reaction temperature. 27.65%(W/W) of HCI concentration. The KS experiment proved that manufactured aluminum chloride hexahydrate was 98.7% degree and the recycled PACI coagulants agreed with the KS standard. The optimum temperature of decomposition was $180^{\circ}C$ and the basicity of the PACI was decided upon the extent of decomposition The compared experiments between purchased coagulant and manufactured coagulant presented that both coagulants had same performance for turbidity, DOC, $UV_{254}$ absorbance. and chlorophyll-a.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.55-60
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• 1984

An experiment on the efficiency of soybean meal substituted for fish meal in the diet of common carp was carried out at the Fish Culture Experiment Station of the National Fisheries University of Pusan from June 27 to August 25, 1983. The carp used for the experiment were 50 fish each lot, each averaging 26 g in initial weight (total weight 1300 g). The experimental diets contained $10\%,\;20\%,\;30\%$, and $40\%$ soybean meal ($44\%$-protein) at iso-protein content basis in place of white fish meal in the control diet which contained $35\%$ protein. The growth rate in the control division was highest with progressive decrease in performance of the fish with increasing rates of soybean meal substituted in the test diets. Nevertheless, the $10\%\;and\;20\%$ soybean meal test diet groups showed acceptable conversions and growth rates, i. e. feed coefficients being 1.28 and l.30 and daily growth rates, $1.708\%\;and\;1.694\%$ compared to $1.22\%\;and\;1.758%$ for the control group, respectively. Therefore, soybean meal could be substituted for fish meal in carp diet by $20\%$ without significant differences of performance with some saving in feed cost.

• Journal of Convergence for Information Technology
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• v.8 no.1
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• pp.9-14
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• 2018

The purpose of this study was to privide basic data for footwear development according to walking mechanics by comparing gait cycle difference between barefoot walking and walking shoes. The walking period was measured in 30 normal adult women with no foot deformity and abnormality. The first subject walked in sneakers and measured the cycle. And then, the subjects walked barefoot and the period was measured to obtain data. The data were taken form corresponding paired T-test. The results were as follows: In barefoot walking, the stance phase left side(p <.001), right side(p <.005), the loading response left side(p <.009), right side(p <.002) ), the pre-swing left side(p <.002), right side (p <.011), the double stance phase(p <.004) were increased and the mid-stance left side (p <.016), right side(p. 001), the swing phase left side(p<.001) was decreased. This suggests that barefoot walking increases the input of various senses of the foot, which makes stable walking possible. It is necessary to improve shoes based on the walking cycle in the future.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.389-397
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• 1992

Workability and aging behavior of Mg-Li-Al alloys hate been investigated with variation of Li and Al contents. It was found that ${\alpha}$(HCP) + ${\beta}$(BCC) two phase structure reveals better workability than ${\alpha}$(HCP) single phase structure. Increase of workability is attributed to the additional slip on pyramidal and prism planes besides the slip on basal plane of HCP Mg. Workability of ${\alpha}$+${\beta}$ two phase structure is improved with increased amount of Al. Among alloys studied in the present study, reduction limit up to 62 % was obtained for Mg-8.08Li-4.26Al. MgL$i_2$Al(${\theta}$) aging precipitation was observed in ${\alpha}$+ ${\beta}$ two phase structure, while it was not in a single phase structure. Result of microhardness reveals peak hardness for ${\alpha}$ +${\beta}$ two phase structure due to $\theta$ precipitate in ${\theta}$ phase. In ${\alpha}$+${\beta}$ two phase Mg-Li-Al alloys, hardness increased with increasing amount of Al. It is believed that addition of Al raised the amount Al partition in u phase and ${\theta}$ precipitation in ${\beta}$ phase.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.5 no.2
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• pp.45-49
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• 1972

The following are some results obtained from a series of experiments in rotifer culture and its usage for the food of tiny fish fry: 1, Outdoor concrete ponds, each being $16m^2$, were used to culture the rotifers, Brachionus calyciflorus, and Filinia longiseta. Brachionus calyciflorus usually attained the population of about 100 individuals per ml of pond water. Dipterex was usually applied to control Daphni,a and other crustaceans that generally appear and feed on rotifers. A concentration of 0.16 to 0.2 ppm in the pond water was sufficiently effective to control these natural enimies of rotifers. Poultry dung was very effectively used to multiplicate rotifers. The fertilization ratio was about 8 kg each pond with 30cm depth of water. 2. The tiny rotifer, Filinia longiseta attained a very high population density of about 1,000 individuals per ml of pond water, but they were very sensitive to dipterex, and for this aspect future investigation may be needed. 3. In the outdoor ponds, the multiplication of rotifers significantly decreased when the water temperature falls to about $20^{\circ}C$ in autumn. 4. In the laboratory room, unicellular planktonic algae such as Scenedesmus or Chlorella, as the food of rotifers, were collected from the outdoor ponds by dipping them together with water, and were effectively used for the culture of Brachionus calyciflorus. If the planktonic algae are cultured in specially designed containers, the sun-light would be the most effective means as the source of light. 5. Brachionus calyciflorus cultured in the outdoor ponds by the dipterex controlled method was highly efficient to rear the early fry of marble gourami. The dipterex content mixed in the water to control the crustacean emmies of rotifers sieved no harm to the gourami fish fry.

• Journal of Aquaculture
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• v.10 no.3
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• pp.335-346
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• 1997

Denitrification is one of the important processes of removing nitrate from in recirculating aquaculture systems. And this process is affected by many factors such as external organic carbon sources, hydraulic retention time (HRT), COD/NO3--N (C:N) ratio, etc. However, not many studies were done for the optimum conditions of denitrification in the recirculation system for aquaculture. Therefore, this study was conducted to find out the optimum removal condition of NO3--N using submerged denitrification biofilter. The combinations of two external organic carbon sources (glucose and methanol), two HRT (4 and 8-hour) and four differnent C : N ratios (3, 4, 5, 6) were tested. The removal efficiencies of NO3--N and total inorganic nitrogen (TIM) at 8-hour HRT were better than those at 4-hour's (P<0.05). The maximum removal efficiency of NO3--N by methanol (97.8%) was achieved at HRT and C : N ratio were 8-hour and 4.0 respectively. The efficiencies of methanol for the removal of NO3--N and TIN were always better than those of glucose (P<0.05). The maximum removal efficiencies of total inorgainc nitrogen (TIN) were gained at C : N ration of 5.0. The maximum removel efficiencies of TIN using methanol and glucose were 96.9% and 71.5% respectively. Anaerobic condition which is necessary for denitrification process was not made until the 8-hour HRT and higher C : N ratio (5.0). Removal of NO3--N at 4-hour HRT and C : N ration lower than 5.0 were inhibited by oxygen and/or low quantity of external organic carbon. Removal efficiencies of NO3--N were also inhibited by high C : N (6.0) ratio when HRT was 8-hour.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.7 no.2
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• pp.69-78
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• 1974

A study on the contents of dissolved oxygen and phytoplankton in the pond water has been carried out to determine the water quality and to investigate the cause of red water in fish ponds at Pusan Fisheries College in 1972-1973. The results obtained are as follows : 1. Measured oxygen content during the period from 6th to 7th of August 1972 was: 23.95ppm ($328\%$ in saturation rate) in daytime and 0.39 ppm($5\%$) in the early morning in the water which contains heavy bloom of phytoplankton, on the other hand, in clear water the range of oxygen content was 8.72 to 6.58ppm. 2. The occurrences of red water in 1972-1973 were always caused by the sudden death of Synechocystis aquatilis (Cyanophyta) when the water temperature was very high ($30-33.5^{\circ}C$) and then high mortality of fish under rearing followed. 3. The phytoplankon observed during this study period was 133 species belonging to 55 genera in 23 families, and those of Chlorophyta was dominant in number of species, and Cyanophyta in quantity. 4. Zooplankton observed was 12 species belonging to 11 genera in 11 families, and they were very small both in number of species and in quantity compared to those of phytoplankton.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.257-259
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• 1976

An experiment on the growth of common carp by feeding low (animal) protein feed when stocked at a rotatively low rate of density was conducted in 1976 at the fish pond of the National fisheries University of Busan. Three ponds averaging $454m^2$ were used with rations of different combinations of feed in respect to protein content. Each pond was equally stocked with 72 general common carp averaging 81.2g and 28 colored common carp averaging 37.8g and the fish were fed for 189 days. In the first pond where the feed with $20\%$f ish meal content ($19.0\%$ crude protein) was fed, the general common carp grew to 776.2g average (63 survived), colored common carp to 504.2g (24 survived), and total average to 701.1g (87 survived). In the second pond where $35\%$ fish meal feed ($27.3\\%$ crude protein) given, the fish grew to 792.9g (70 survived), 539.1g (23 survived) and 730.1g(93 survived), respectively, and in the third pond where $50\%$ fish meal feed ($34.6\%$ crude protein) given, the fish grew to 983.7g (49 survived), 630.4g (23 survived) and 870.8g (72 survived), respectively. A significant mortality during the experiment was due to an accidental introduction of Trichodina and Dactylogyrus infected with the stocked fish under experiment at the beginning. In this experiment the rate of harvest per hectare was very low being 1,352kg, 1,495kg and 1,447kg respectively which is tess than half of the yield at general commercial fish ponds. Therefore, it is concluded that at this rate of reduced production trial, the content of protein in the feed must not be cut down from the normal level.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.261-263
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• 1976

In 1975, a trial for channel catfish spawning was made for the first time in Korea, by stocking 11 pairs of brood fish in a $470m^2$ earthen pond provided with 5 cans of 35 cm in diameter with depths of about 60 cm as spawning nests. The same trial and another pen cage method combined with pituitary injection were practiced in 1976. All these trials failed without any spawning. On the other hand 4 females and 1 male were put in a recycling water system indoor aquarium for exhibition purpose it late spring of 1976. After removing 3 females which were injured from being bitten by the male, remaining one pair of the catfish spawned successfully in July and the most eggs developed normally. The water in the recycling system showed the pH range of 7.2 to 7.4,and mean water temperature of every 10 day period of a month gradually increased from 19.3 to 23.6C until spawning. The outdoor .ponds where the spawning was failed received water from the same origin as the indoor recycling system, and the mean temperature of every ten day period ranged Iron 17.2 to $29.8^{\circ}C$ in 1975 and 19.7 to $28.4^{\circ}C$ in 1976 these being considered well falling in the optimum range for catfish spawning, but pH ranged from 7.3 to 9.5 under the influence of photosynthesis of algae and weeds in the ponds. The high pH value may suppress the spawning of catfish as pointed out by Nelson in 1957.